4 GiB on Asus A8N-SLI Deluxe

[gzunk]

Does anyone know what options I need in the kernel to get this working? There are two BIOS options that are relevant, SW Memory Remap and HW memory remap. If I choose SW Memory Remap only, then BIOS reports 3GiB out of 4GiB usable and I can use 3GiB and everything works fine. If I choose the HW memory remap then BIOS reports 4GiB out of 4GiB usable, but the kernel panics on boot.

Any ideas?
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Intel Core 2 Quad Q9650 | Asus P5K | 8GB DDR-2 800
Sapphire Radeon 4870 X2 | 30" Samsung SM305T+
(4xSATA) 3 TB | 2 x DVD+-RW DL (Pioneer 112D 115D)
Logitech X-530 5.1 | DiNovo Edge | MX Revolution

[phant0ml0rd]

In a 32bit system, the maximum addressable memory space is 2^32 = 4 GiB. Now in a regular computer, the upper portion of the addressable space is reserved for peripherals. Those dual 7800 GTX's for example eat up a bunch of that space. When you choose to do SW remap, the BIOS presents the entire 4 GiB space minus the reserved space for peripherals, resulting in ~ 3GiB usable that you see. When you do a HW remap, it gets more tricky, some BIOS's use re mapping hacks to make the second 2 GiB visible after the 4GiB. Theoretically, it is supposed to make your OS seem to think there are 6 GiB of which 4 are usable. I have never heard of this working correctly though.

Anyway, the solution to your problems would be to switch to a 64 bit version of gentoo.